Taittiriya Upanishad 3.8.1

3.8.1

annaṃ na paricakṣīta /
tadavratam /
āpo vā annam /
jyotirannādam /
apsu jyotiḥ pratiṣṭhitam /
jyotiṣyāpaḥ pratiṣṭhitāḥ /
tadetadannamanne pratiṣṭhitam /
sa ya etadannamanne pratiṣṭhitaṃ veda pratitiṣṭhati /
annavānannādo bhavati /
mahānbhavati prajayā
paśubhirbrahmavarcasena /
mahān kīrtyā // 1//
ityaṣṭamo 'nuvākaḥ //

His vow is that he should not discard food. Water, indeed, is food; fire is the eater; for water is established on fire. (Fire is food and water is the eater, for) fire resides in water. Thus one food is lodged in another food. He who knows thus that one food is lodged in another, gets firmly established. He becomes a possessor and an eater of food. He becomes great in progeny, cattle, and the lustre of holiness, and great in glory.